This paper reports a voltage regulation method with power management to enhance the reliability and stability of the self-powered flow rate sensor. Triboelectric energy harvesters are used both as the sensing signals and the power supply. One channel of the raw voltage from wind flow is regulated to a stable signal by the integral circuit, while the other channel is used for energy harvesting to provide the power for the whole circuit. Power management chip with ultra-low power consumption has been utilized with micro controller unit and antenna for wireless transmission. A low deviation of less than 2.5% has been achieved for the flow sensing signal and the temperature has also been monitored simultaneously, which shows promising application for the central air-conditioning system in smart buildings.

Introduction

Wireless sensor networks (WSN) have attracted more and more attentions for wide applications in the fields of industry, healthcare, and environmental monitoring, etc. Recently, another concept of ‘‘Internet of Things (IoT)’’ has also been developed, which typically consists of WSN, cameras, smartphones, and RFIDs, to collect data and track information for smart city [1], smart home [2], intelligent buildings [3], and industrial Internet of Things (IIoT) [4], [5]. However, the service life of WSN and IoT are limited by traditional batteries with finite capacity. Hence, they need other technology to solve this problem and prolong the life of themselves. Energy harvesting (EH) technology has been developed in the past decade, as it can extract energy from ambient environment to replace the batteries [6], [7]. Vibration based energy harvesters can be typically achieved by four principles, piezoelectricity [8]–[۱۳], electromagnet [14]–[۱۶], electrostatic [17]–[۲۰] and triboelectricity methods. Piezoelectric EH utilizes the deformation of piezoelectric film to generate power. Faraday’s law of electromagnetic induction is the basic principle of electromagnet EH. Electrostatic EH output alternate voltage by changing the overlapping area or gap distance of capacitors with electret material, which can store the charge for a long period of time. Recently, increasing research efforts have been made in water flow and wind flow EH field, because wind and tidal energy are important clean energy resources in the environment. For instance, Shan et al. [21] presented a double piezoelectric energy harvesters (DPEH) system to scavenge energy underwater.